Multi-signal explosive detonator



1966 F. A. eoss, JR

MULTI-SIGNAL EXPLOSIVE DETONATOR Filed June 15, 1965 INVENTOR. Frank A. 605.9, Jr.

A Horney Unite States The present invention relates generally to explosive detonators, and more particularly to electrical initiators for use in explosive detonators wherein the simultaneous presence of a plurality of electrical signals are necessary to actuate the electrical initiator.

Explosive detonators using electrical initiators such as bridge wires or resistance wires for converting electrical energy into heat energy in response to the application of a single electrical signal at the initiator suffer a significant drawback or shortcoming in that inadvertent actuation of such initiators is relatively easily achieved. This objectionable initiator actuation may occur in any of several different ways, such as, for example, accidental energization or closing of the single initiator firing circuit such as caused by operator carelessness, malfunction of the firing circuit, impact loadings upon the firing circuit, or the presence of spurious electrical signals in the firing circuit due to electromagnetic radiation in the form of radio waves or the like.

The present invention aims to obviate or minimize the above and other drawbacks or shortcomings of previous electrical detonators by providing an explosive detonator embodying an electrical initiator actuable only in response to the simultaneous or concurrent presence of two separately applied electrical signals such that the presence of either one or the other electrical signal at the initiator is ineffective to initiate the explosive of the detonator. The novel initiator of the present invention utilizes a semiconducting device in the explosive detonator in place of the bridge wire, resistance Wire, or other type electrical initiator. Current flow through the semiconducting device rapidly raises the temperature of the latter up to and above the ignition temperature of the explosive, but such current flow cannot occur until an electrode of the device is prow'ded with a suitable electrical potential representing the first electrical signal while another electrode, i.c., a gate or control electrode, is provided with a suitable voltage or signal representing the second signal during the application of the first signal. The advantages of the present two-signal explosive initiator are believed to be quite evident in that no single electrical signal can actuate the initiator as in the previous devices. Also, spurious electrical signals in the initiator leads such as caused by electromagnetic radiation are not detrimental since electromagnetic coupling is a function of circuit configuration and orientation which, in the present case, would I be physically different such that the probability of both circuits being resonant to provide the necessary simultaneous signals is extremely remote.

An object of the present invention is to provide a new and improved initiator for an explosive detonator.

Another object of the present invention is to provide an improved electrical heating means for use as an initiator in an explosive detonator.

Another object of the present invention is to provide an explosive detonator actua'ble only in response to two coincident electrical signals.

A further object of the present invention is to provide an electrical initiator for an explosive detonator that is substantially safer and vmore reliable than previous initiators.

A still further object of the present invention is to atent provide an electrical initiator configuration affording substantial miniaturization.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiments about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

Preferred embodiments of the invention have been chosen for purposes of illustration and description. The embodiments illustrated are not intended to be exhaustive nor to limit the invention to the precise forms disclosed. They are chosen and described in order to best exp-lain the principles of the invention and their application in practical use to thereby enable others skilled in the art to best utilize the invention in various embodiments and modifications as are best adapted to the particular use contemplated.

The explosive material used in the detonators hereinafter described may be of any suitable type ranging from relatively slow combustible materials up to highly detonatable materials; which range includes relatively insensitive or secondary explosive material such as cyclotrimethylene trinitramine (RDX) and relatively sensitive or primary explosive material such as lead styphnate. Accordingly, the term explosive charge or explosive material as used herein is not intended to be limited to a particular class of detonatable materials. While the multisignal initiator of the present invention is described as being used with explosive detonators, it is to be understood that the initiator may be used with other devices, such as, for example, squihs, ignitors, and the like.

In the accompanying drawing:

FIG. 1 is a perspective view, partly cut away, showing an explosive charge and semiconductor initiator of the present invention;

FIG. 2 is a perspective view, partly cut away, showing another form of the semiconductor initiator as it may appear in an explosive detonator;

FIG. 3 is a fragmentary plan view showing the semiconductor initiator of FIG. 2 with the initiator enlarged for ease of illustration; and

FIG. 4 is an enlarged elevational sectional view taken generally along line 44 of FIG. 3.

With reference to FIG. 1 there is shown an electrically actuable explosive detonator assembly It) which may comprise a multiple layer semiconductor initiator 12 secured by soldering, adhesives, or other suitable means to a base or support 14 and partially covered with an explosive charge 16. The semiconductor initiator may be electrically coupled to a suitable energy source or sources through electrical terminals 18, 1) and it which may be carried by and project through the base 14 with an end of terminal 18 providing an electrode contact with the bottom layer of the semiconductor while the other two terminals 19 and 29 may be connected to other layers of the semiconductor initiator by lead wires or electrodes 22 and 24 respectively. These lead wires may be electrically joined to the initiator and the terminals in any suitable manner such as by soldering or the like. If the base 14 is of conducting material it may be preferable to electrically isolate terminals 19 and 2t therefirom such as by insulating tubulations as shown at 25.

The semiconductor initiator 12 may comprise any suitable semiconductor construction containing one or more PN junctions which provide depletion regions or barriers which, in turn, effect heating of the semiconductor material particularly adjaccnt the PN junction upon the passage of current in the semiconductor. For example, an ordinary junction transistor may be used but it may be preferable to use silicon or germanium power transistors or rectifiers because of the greater power transfer attainable with such devices. By way of illustration the initiator 12 in FIG. 1 is shown as a four-layer silicon control rectifier which may comprise stacked layers 28, 29, 30, and 31 of silicon with alternate layers 28 and 30 containing N- type impurities while layers 29 and 31 contain P-type impurities. Layer 29 may have a central portion thereof removed for receiving layer 28 which may have an upper surface thereof substantially common with the upper surface of layer 29. Wit-h this construction a substantial portion of the PN junction of layers 28 and 29 is in close proximity to or in registry with the upper surface of the initiator and in contact with and underlying the explosive charge 16, thus facilitating the heating of the explosive char-go 16.

The explosive charge 16, which may be of any suitable explosive material, such as, for example, potassium dinitrobenforaxan (KDNBF), may be formed with a pastelike consistency and spread onto layer 28 and adjacent portions of layer 29. While the explosive charge 16 is shoWn as being of a relatively small quantity it is to be understood that such showing is merely for illustration purposes and that any desired quantity of the explosive charge 16 may be placed in contact with the semiconductor initiator. Also, the explosive charge need not be buttered onto the semiconductor as a paste-like substance, since the initiator functions equally well with an explosive charge in powder form which may be placed in contact with the semiconductor such as by pressure loading. Further, a suitable housing (not shown) may be secured to support 14 so as to enclose the initiator 12 and explosive charge 16.

As pointed out above, the explosive initiator of the present invention is capable of detonating the explosive only in response to two separately applied electrical signals which must at some point of time during their application coexist on the initiator. In order to provide this multi-signal feature, the lead wire 24 may be attached to layer 28, which attachment is preferably made prior to placement of the explosive charge 16, and coupled to terminal 20 while layer 31 is coupled to terminal 18 as above described. These terminals, in turn, may be electrically coupled to a suitable power supply such as a battery or the like (not shown) via a suitable firing circuit closing system (not shown) for supplying electrical energy to the initiator to establish current flow therein for heating the initiator 12 to eifect detonation of the explosive charge 16. Inasmuch as this current flow in the initiator cannot occur until the latter receives a separately applied electrical control signal which overlaps or is overlapped by the signal through terminal 18, the layer 29 of the initiator may be electrically coupled through lead wire 22, terminal 19, and another firing circuit closing system (not shown) to a suitable power supply which may be different from or the same power supply used to provide current flow in the initiator.

For exemplary purposes the FIG. 1 device may be actuated in the following manner. The circuit closing system for supplying the layer 31 with electrical energy may be actuated such as by closing a switch or in response to some operating condition to impose an electrical potential on the layer 31. At some point in time, which may be before, after or simultaneously with the initial application of the electrical potential on the layer 31, the circuit closing system for supplying the control signal to layer 29 may be actuated such as by closing a switch or in response to some other operating condition to influence the barrier or depletion regions between layers 28 and 31 for enabling current flow through the PN junctions to rapidly heat the initiator 12 to the detonation temperature of the explosive charge 16. The strength of the control signal affects the quantity of current flow in the initiator which, in turn, is proportional to the heating of the PN junctions. Thus, the initiator is preferably provided with a large control signal voltage to assure sufiicient current 1.5 flow through the initiator for rapidly heating the latter to the ignition temperature of the explosive'charge.

In FIGS. 2, 3 and 4, there is shown an explosive detonator 35 embodying a preferred form of a semiconductor initiator in which all the PN junctions therein are in registry with an upper surface of the initiator to provide an initiator construction wherein substantial miniaturization may be effected while providing sufficient surface area to attach electrodes.

Referring more particularly to FIG. 2, the detonator 35 may comprise a tubular case or housing 37 containing an explosive charge 38 and secured to peripheral surfaces of a disc-shaped base 39, which, in turn, carries semiconductor initiator 41 and electrical terminals 43, 44 and 45. The case 37 and the base 39 may be constructed of any suitable material in any suitable manner. For example, a relatively hard and strong metal such as stainless steel or a softer metal such as gilding metal may be drawn into the desired configuration to provide a suitable housing structure while the base 39 is preferably of an electrical insulating material, e.g., glass or ceramic. With the case and terminals of metal and the base of glass adequate connections therebetween may be readily attained by utilizing any suitable glass-to-metal seal.

As shown in FIG. 4, the semiconductor initiator 41 may comprise four coaxially disposed silicon layers or portions 47, 48, 49 and 50 With portions 47 and 4-9 containing N-type impurities while portions 48 and 50 contain P- type impurities. These silicon portions may be carried by a silicon P+ layer 52 for power transfer purposes with the layer 52 adhesively secured to the base 39 by any suitable adhesive material having low thermal conductivity. The initiator is so constructed that the various silicon portions are in registry with a common surface, i.e., the upper surface of the initiator. This construction assures that each layer is provided with sufiicient exposed surface area to attach electrodes while at the same time facilitating extensive miniaturization.

The initiator 41, which may be of a generally polygonal configuration such as shown and have an upper surface area of about 0.0003 of a square inch, may be formed by initially providing the P-llayer 52 with the layer 50 by using a suitable epitaxial growth process. The combined thickness of layers 50 and 52 may be about 0.003 of an inch with layer 50 comprising about one-eighth of this thickness (layer 52 is shown thinner than layer 50 for illustration purposes). A suitable template or coating, such as, for example, a coating of silicon dioxide provided by exposing silicon layer 50 to a wet oxygen environment at high temperatures may be placed over the exposed surface of layer 50. A suitable etching solution may then be applied to the silicon dioxide coating to expose a generally circular central section of the layer 50 of about 0.011 of an inch in diameter. N-type impurities may then be diffused into layer 50 to convert or change preferably the entire central portion of layer 50 to N-type silicon for forming layer 49 which is separated from layer 50 by side walls 51 transversally disposed with respect to layer 52 to define a first PN junction between layers 49 and 50. A new silicon dioxide coating may then be applied over layers or portions 49 and 50. The etch solution may then be used to remove a circular central section of the silicon dioxide coating overlying layer 49 to provide an exposed surface of about 0.009 of an inch in diameter. This exposed central portion may then be subjected to diffusion of P-type impurities extending to about one half the thickness of layer 49 for defining layer 48. The above silicon dioxide recoating step may then be repeated. A circular central section of the silicon coating overlying layer 4-8 may then be removed to expose a surface of layer 48 having a diameter of about 0.003 of an inch. About half the thickness of this exposed portion of layer 48 may then be diffused with N-type impurities to form layer 47. PN junctions are defined between layers 47 and 48 and layers 48 and 49 in a manner similar to the PN junction between layers 49 and 50.

Inasmuch as the initiator is thin, the diffusion of the various layers with N or P-type impurities to the desired depth may be achieved by timing the exposure of the layer to the diffusion. Also, the particular dimensions noted for the various layers are not critical but are merely exemplary of initiator dimensions providing suitably sized depletion regions which may be used.

Electrodes for the various silicon layers may be provided by vacuum depositing aluminum or other suitable conducting metal onto the upper surfaces of the layers. As best shown in FIGS. 3 and 4 the electrodes are deposited onto silicon layers 47, 48 and 50 with the electrode 55 for layer 48 extending as a straight strip from one corner of the initiator to the center of layer 48 While electrodes 57 and 58 for layers 48 and 50, respectively,"

similarly extend from other corners of the initiator as straight strips to the particular layers. The electrodes 55 and 57 are electrically insulated from underlying layers except for the particular layers to which electrical couplings are desired as will be brought out below. In order to assure good electrical couplings between the electrodes 57 and 58 and the underlying layers .8 and 50 sections of the electrodes may circumferentially extend about the surface of the layers. For example, the section of electrode 57 on layer 48 is shown in the form of a 270 circular segment or are with the space between the spaced apart ends of the arc accommodating the electrode strip 55. The section of electrode 58 on layer 50 is likewise shown in the form of circular segment or arc but may cover only 210 of the layer 50 so that the open space between the electrode section ends may accommodate electrodes 55 and 57. These particular circumferential dimensions for the electrodes 57 and 58 are not critical since other electrode dimensions may be used to provide adequate electrical couplings.

In vacuum depositing these electrodes, the surface of the silicon layers may be masked to provide contacts of about 0.001 of an inch wide in the desired configuration. Inasmuch as the surfaces of the silicon layers are oxidizable, as described above, to provide a coating of electrically insulating silicon dioxide thereover, the contacts may be directly deposited onto the silicon dioxide coatings overlying the layers such that electrodes 57 and 53 are insulatively secured to and carried by several silicon layers. To provide an electrical coupling between an electrode and a desired underlying silicon layer, the unmasked surface portion of the particular layer may be treated by etching solution to remove desired portions of the silicon dioxide coating for assuring that the subsequently deposited electrode is electrically coupled to the underlying layer. While the electrodes are shown as being of slightly less thickness than that of the silicon layers for illustration purposes, they are preferably of about 0.00004 of an inch in thickness.

As shown in FEGS. 2 and 3, the initiator 41 may be positioned on the surface of the base 39 at a location spaced from and generally intermediate the terminals 4345. In order to connect these terminals to the electrodes of the initiator, conductive strips about 0.005 of an inch Wide and of gold or other suitable metal may be vacuum or otherwise deposited onto the base prior to the placement of the initiator onto the base 39. Ends of these conductive strips 62, 63 and 64 adjacent the terminals may be soldered to terminals 43, 44 and 45 respectively, while the other ends are preferably spaced about 0.0015 of an inch from the sides of the initiator. Electrical lead wires cs, 67 and 68 of about 0.001 to about 0.0015 of an inch in diameter may then be secured to conductive strips 62, 63 and 64 respectively, and to initiator electrodes 55, 57 and 58 respectively. The bond between the lead wires and the conductive strips may be a thermal compression ball bond while the bond with the initiator contacts may be a chisel bond, or if desired ultra- 6 sonic welding or any other suitable attachment may be used.

The base assembly including the initiator 41 may be placed into the open end of the explosive filled case 37 such that the initiator is in physical contact with the explosive to assure initiation of the latter upon passing current through the initiator. The base may then be secured to the base such as by projection welding to assure a good seal therewith.

To enhance the operation of the detonator the explosive charge 38 may be pressure loaded at a pressure of about 4000 pounds per square inch for assuring adequate contact with the initiator. The pressure loading may be achieved by placing the explosive filled case 37 in a suitable fixture (not shown) and then pressing the base against the explosive until the desired compaction of the explosive charge is attained.

In the explosive detonating device shown in FIGS. 24, the operation of the initiator 41 is similar to the explosive initiator 12 of FIG. 1, Le, current flow in the initiator 41 for heating the latter will not occur until two separately applied electrical signals from one or more energy sources through suitable control or switching systems are at some point of time coexistent on the initiator. In initiator 41 a current of about 2 amperes may flow between electrodes 55 and 53 in response to an electrical signal of about 24 volts through terminal 45 with such current flow occurring through the initiator only upon application of a suitable coexisting or coincident electrical voltage signal of about 2 to 10 volts and of about to about 200 milliamperes to the gate or control layer 48 through terminal 44.

Like in the FIG. 1 device, the greater the voltage applied to the layer 48, the greater the current fiow through the PN junctions and the faster the rise time in initiator temperature. Usually, the semiconductor initiator such as initiator 12 or 41 has a rise time to a temperature sufficient to detonate the explosive charge, whether it be of primary or secondary type, of about one millisecond.

While the initiator of the present invention has been described as being actuable in response to two coincident electrical signals it is to be understood that more than two such signals may be used to effect actuation of the initiator. To achieve this feature with the FIGS. 2-4 device, for example, the layer 48 may be provided with more than one electrode-say, for example, two electrodes, so that the additive signal coincidently applied to layer 43 through the two electrodes is sufiicient to efiect current conduction through the initiator in response to an electrical signal on layer 50 which, in turn, is consistent with the two signals on layer 48.

It Will be seen that the electrical explosive initiator of the present invention represents significant advancements over previously known electrical explosive initiators particularly in the area of safing in that the previous bridge wire and resistance wire initiators were operable in response to a single electrical signal, whereas with the present initiator at least two separate signals must be applied with the signals coincident or overlapping. Also, the initiator of the present invention provides greater miniaturization of electrical initiators than attainable with previous devices. The ignition element of the present invention may be utilized to initiate larger explosive charges, ignite solid propellants, or in any other desired manner.

As various changes may be made in the form, construction and arrangement of the parts herein Without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A multi-signal explosive detonator comprising an initiator including a plurality of interconnected portions of semiconducting material incorporating N-type and P-type impurities in adjacent portions to define PN junctions therebetween, an electrode electrically coupled to one of said portions; other electrodes electrically coupled to other said portions spaced apart from each other by at least said one portion for providing current flow in said semiconducting material to heat the latter in response to an electrical signal through at least one of said other electrodes and only during the application of another coexisting electrical signal through the first mentioned electrode, and an explosive charge disposed in an abutting relationship with at least one of said portions.

2. The multi-signal explosive detonator claimed in claim 1, wherein said initiator is secured to a support member, terminal means are carried by said support member, and wherein said terminal means are electrically coupled to said electrodes.

3. The multi-signal explosive detonator claimed in claim 2, wherein a housing is secured to said support member enclosing said initiator and explosive charge, and

References Cited by the Examiner UNITED STATES PATENTS 3,211,096 10/1965 Forney et al. 10228 BENJAMIN A. BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

1. A MULTI-SIGNAL EXPLOSIVE DETONATOR COMPRISING AN INITIATOR INCLUDING A PLURALITY OF INTERCONNECTED PORTIONS OF SEMICONDUCTING MATERIAL INCORPORATING N-TYPE AND P-TYPE IMPURITIES IN ADJACENT PORTIONS TO DEFINE PN JUNCTIONS THEREBETWEEN, AN ELECTRODE ELECTRICALLY COUPLED TO ONE OF SAID PORTIONS, OTHER ELECTRODES ELECTRICALLY COUPLED TO OTHER SAID PORTIONS SPACED APART FROM EACH OTHER BY AT LEAST SAID ONE PORTION FOR PROVIDING CURRENT FLOW IN SAID SEMICONDUCTING MATERIAL TO HEAT THE LATTER IN RESPONSE TO AN ELECTRICAL SIGNAL THROUGH AT LEAST ONE OF SAID OTHER ELECTRODES AND ONLY DURING THE APPLICATION OF ANOTHER COEXISTING ELECTRICAL SIGNAL THROUGH THE FIRST MENTIONED ELECTRODE, AND AN EXPLOSIVE CHARGE DISPOSED IN AN ABUTTING RELATIONSHIP WITH AT LEAST ONE OF SAID PORTIONS. 